Lens cover having lens element

ABSTRACT

A lens cover for a plurality of light emitting devices is provided. The lens cover includes a base substrate and an optical lens element. The optical lens element extends from the base substrate and defines a focal center. The optical lens element includes a length and a width and includes an exterior surface and interior surface. The exterior surface extends from the base substrate along an outer perimeter and is symmetrical about the focal center. The interior surface is symmetrical about the focal center.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/591,257, filed Feb. 2, 2022, entitled Lens Cover Having Lens Elementwhich is a continuation of International Application No.PCT/CN2020/132703, filed Nov. 30, 2020, entitled Lens Cover Having LensElement and hereby incorporates these applications by reference hereinin their respective entireties.

TECHNICAL FIELD

The apparatus described below generally relates to a light fixture thatincludes an array of light sources for illuminating an indoor growfacility. Each light source includes a light emitting diode (LED), alens cover, an encapsulating material that is disposed between the LEDsand the lens cover, and a protective coating provided over an exteriorsurface of the lens cover.

BACKGROUND

Indoor grow facilities, such as greenhouses, include light fixtures thatprovide artificial lighting to plants for encouraging growth. Each ofthese light fixtures typically includes a plurality of LEDs thatgenerate the artificial light for the plants. The environment insidethese indoor grow facilities, however, can include different types ofgasses and/or airborne fluid particles that cause the optical quality ofthe LEDs to degrade (e.g., yellow) over time.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will become better understood with regard to thefollowing description, appended claims and accompanying drawingswherein:

FIG. 1 is an upper isometric view depicting a light fixture, inaccordance with one embodiment;

FIG. 2 is a lower isometric view of the light fixture of FIG. 1 ;

FIG. 3 is a partially exploded upper isometric view of the LED lightfixture of FIG. 1 ;

FIG. 4 is a partially exploded lower isometric view of the LED lightfixture of FIG. 1 ;

FIG. 5 is a cross-sectional view taken along the line 5-5 in FIG. 4 ;

FIG. 6 is a schematic view of various components of the light fixture ofFIG. 1 ;

FIG. 7 is a lower isometric view depicting a lens cover for a lightfixture, in accordance with another embodiment;

FIG. 8 is an upper isometric view depicting the lens cover of FIG. 7 ;

FIG. 9 is a sectional view taken along the line 9-9 in FIG. 7 ;

FIG. 10 is a sectional view taken along the line 10-10 in FIG. 7 ;

FIG. 11 is an enlarged top plan view of the lens cover of FIG. 7 ;

FIG. 12 is an enlarged bottom plan view of the lens cover of FIG. 7 ;

FIG. 13 is a sectional view taken along the line 9-9 in FIG. 7 ;

FIG. 14 is a sectional view taken along the line 10-10 in FIG. 7 ; and

FIG. 15 is an IES light distribution plot for the lens cover of FIG. 7 .

DETAILED DESCRIPTION

Embodiments are hereinafter described in detail in connection with theviews and examples of FIGS. 1-15 , wherein like numbers indicate thesame or corresponding elements throughout the views. A light fixture 20for an indoor grow facility (e.g., a greenhouse) is generally depictedin FIGS. 1 and 2 and can include a housing 22, first and second lightingmodules 24, 26 (FIG. 2 ), and a hanger assembly 28. The housing 22 caninclude a light support portion 30 and a controller support portion 32adjacent to the light support portion 30. The light support portion 30can define a lighting receptacle 34 (FIG. 1 ) and a window 36 (FIG. 2 )disposed beneath the lighting receptacle 34. The first and secondlighting modules 24, 26 (FIG. 2 ) can be disposed within the lightingreceptacle 34 above the window 36 and can be configured to emit lightthrough the window 36, as will be described in further detail below.

The hanger assembly 28 can facilitate suspension of the light fixture 20above one or more plants (not shown) such that light emitted through thewindow 36 from the first and second lighting modules 24, 26 can bedelivered to the underlying plant(s) to stimulate growth. The hangerassembly 28 can include a pair of hanger supports 38 and a hangerbracket 40. The hanger supports 38 can be coupled to the housing 22 onopposing sides of the light fixture 20. The hanger bracket 40 can becoupled with the hanger supports 38 and can extend between the hangersupports 38 to facilitate suspension of the light fixture 20 from aceiling of the indoor grow facility. In one embodiment, as illustratedin FIGS. 1 and 2 , the hanger bracket 40 can have a cross-sectionalshape that is substantially J-shaped to facilitate selective hanging ofthe light fixture 20 from a beam or other elongated support member thatis provided along a ceiling of the indoor grow facility.

Referring now to FIGS. 3 and 4 , the housing 22 can include a main frame42 and a cover member 44 that overlies the main frame 42 and is coupledtogether with the main frame 42 via welding, adhesives, releasable tabs(not shown), fasteners (not shown), or any of a variety of suitablealternative permanent or releasable fastening arrangements. The mainframe 42 can include a bottom lighting wall 46 that defines the window36. As illustrated in FIG. 3 , the main frame 42 can include a bottomcontroller wall 48, and a plurality of sidewalls 50 that cooperate todefine a controller receptacle 52. The cover member 44 can include a lidportion 54 that overlies and covers the controller receptacle 52, asillustrated in FIG. 1 . The bottom controller wall 48, the sidewalls 50,and the lid portion 54 can form at least part of the controller supportportion 32 of the housing 22.

As illustrated in FIG. 4 , the first and second lighting modules 24, 26can each include a submount 56, 58, a plurality of light emitting diodes(LEDs) (e.g., 60 in FIG. 5 ), and a lens cover 64, 66. Referring to FIG.5 , the first lighting module 24 will now be discussed, but can beunderstood to be representative of the second lighting module 26. TheLEDs 60 can comprise surface mount LEDs that are mounted to the submount56 via any of a variety of methods or techniques commonly known in theart. The LEDs 60 can be any of a variety of suitable configurations thatare mounted directly or indirectly to the submount 56. The LEDs 60 cancomprise single color LEDs (e.g., capable of emitting only one color oflight such as white, red or blue), multi-color LEDs (e.g., capable ofemitting different colors such as white, red, and blue) or a combinationof both. The submount 56 can be formed of any of a variety of thermallyconductive materials that are suitable for physically and thermallysupporting the LEDs 60. In one embodiment, the LED 60 can be a squareLED that is about 3.5 mm wide and about 3.5 mm long.

The lens cover 64 can overlie the submount 56 and the LEDs 60 and can becoupled with the submount 56 with fasteners 67 or any of a variety ofsuitable alternative coupling arrangements. The lens cover 64 caninclude a base substrate 68 that is substantially planar and a pluralityof optical lens elements 70 that protrude from the base substrate 68.Each of the optical lens elements 70 can be substantially aligned withrespective ones of the LEDs 60 and can be configured to redistribute(e.g., concentrate or disperse) the light emitted from the LEDs 60towards an area beneath the light fixture 20 (e.g., towards one or moreplants). In one embodiment, as illustrated in FIGS. 4 and 5 , each ofthe optical lens elements 70 can have an indented oval shape. However,the optical lens elements 70 can be any of a variety of suitablealternative shapes or combinations thereof for achieving a desiredredistribution of light emitted from the LEDs 60.

As illustrated in FIG. 5 , the LEDs 60 can each be aligned withrespective ones of the optical lens elements 70 such that the physicalcenter P and the focal center F are coaxial. In another embodiment, theLEDs 60 can each be slightly offset with respective ones of the opticallens elements 70 such that the physical center P and the focal center Fare non-coaxial. In one embodiment, the lens cover 64 can have a unitaryone-piece construction formed of a polycarbonate material and/orpolymethyl methacrylate (PMMA). It is to be appreciated, however, thatthe lens cover 64 can be formed of any of a variety of suitablealternative translucent or transparent materials that can protectunderlying LEDs from environmental conditions and can also accommodate aplurality of optical lens elements 70 for redistributing lighttransmitted from underlying LEDs.

The lens cover 64 can be spaced from the submount 56 such that the lenscover 64 and the submount 56 cooperate to define an interior 72therebetween. An encapsulating material 74 can be provided within theinterior 72 such that the encapsulating material 74 substantially fillsthe interior 72 and encapsulates the LEDs 60 therein. The encapsulatingmaterial 74 can be formed of an optically neutral (or enhancing)material that reduces optical loss in the interior 72 that mightotherwise occur without the encapsulating material 74 (e.g., if therewas air in the interior 72). In one embodiment, the interior 72 can befilled with enough of the encapsulating material 74 (e.g., filledentirely) to cause the interior 72 to be substantially devoid of airbubbles or other media that would adversely affect the optical integritybetween the LEDs 60 and the lens cover 64. The encapsulating material 74can also protect the LEDs 60 from environmental conditions that might beable to bypass the lens cover 64 such as a gaseous fluid (e.g.,greenhouse gas). In one embodiment, the encapsulating material 74 can bea silicone gel such as a methyl type silicone (e.g.,polydimethylsiloxane) or a phenyl-type silicone, for example, that has arefractive index of between about 1.35 and 1.6. It is to be appreciatedthat any of a variety of suitable alternative materials are contemplatedfor the encapsulating material 74.

The encapsulating material 74 can be substantially softer than the lenscover 64 (e.g., the encapsulating material 74 can have a hardness thatis less than a hardness of the lens cover 64). In one embodiment, theencapsulating material 74 can be a flowable material, such as a fluid orgel that can be injected or otherwise dispensed into the interior 72after the lens cover 64 is assembled on the submount 56. In anotherembodiment, the encapsulating material 74 can be coated onto the lenscover 64 and/or over the submount 56 and LEDs 60 prior to assembling thelens cover 64 on the submount 56.

Still referring to FIG. 5 , a protective coating 76 can be provided overan exterior surface 77 of the lens cover 64. The protective coating 76can be hydrophobic, oleophobic, and/or chemically resistant such thatthe exterior surface of the lens cover 64 is protected from harmfulenvironmental conditions that might otherwise adversely affect theoptical performance of the optical lens elements 70. The protectivecoating 76 can additionally or alternatively optically enhance thetransmission quality of the optical lens elements 70. In one embodiment,the protective coating 76 can be a thin-film inorganic material thatprotects against environmental conditions (e.g., chemical etching) andalso improves overall transmission quality of the optical lens elements70. The thin-film inorganic material can be between about 10 nm andabout 200 nm thick and can have a refractive index above about 1.49.Some examples of suitable thin-film inorganic materials include MgF2,CaF2, SiO2, Al2O3 and/or TiO2. Although the protective coating 76 isshown to be a single layer arrangement, it is to be appreciated that theprotective coating 76 can alternatively be a multi-layer arrangementthat is either homogenous (multiple layers of the same material) orheterogeneous (multiple layers of different material).

It is to be appreciated that the light emitted by the first lightingmodule 24 can conform to a lighting profile (e.g., range of color,overall distribution of light, heat profile) that is defined by thephysical configuration of the first lighting module 24 (e.g., the typesof LEDs 60 that are utilized (e.g., single color or multi-color), thephysical layout of the LEDs 60, the optics provided by the optical lenselements (e.g., 68), the encapsulating material (e.g., 74), theprotective coating (e.g., 76), and the overall power consumption).Although various examples of the physical configuration of the firstlighting module are described above and shown in the figures, it is tobe appreciated that any of a variety of suitable alternative physicalconfigurations of the first lighting module 24 are contemplated forachieving a desired lighting profile.

Referring now to FIGS. 1 and 3 , a heat sink 78 can be disposed overeach of the first and second lighting modules 24, 26 and can beconfigured to dissipate heat away from the first and second lightingmodules 24, 26. The heat sink 78 can be formed of any of a variety of athermally conductive materials, such as aluminum or copper, for example.The heat sink 78 can be in contact with the submounts 56, 58 on anopposite side from the LEDs (e.g., 60). Heat generated by the LEDs(e.g., 60) can be transferred from the submounts 56, 58 to the heat sink78 and dissipated to the surrounding environment by a plurality of fins80. In one embodiment, a heat sink compound (not shown), such as thermalpaste, for example, can be provided between the submounts 56, 58 and theheat sink 78 to enhance the thermal conductivity therebetween. Althoughthe heat sink 78 is shown to be a unitary component that is providedover the first and second lighting modules 24, 26, it is to beappreciated that dedicated heat sinks can alternatively be provided foreach of the first and second lighting modules 24, 26.

Referring now to FIG. 3 , a controller 82 can be disposed in thecontroller receptacle 52 and can be configured to power and control thefirst and second lighting modules 24, 26. As illustrated in FIG. 1 , thelid portion 54 of the cover member 44 can overlie the controllerreceptacle 52 and the controller 82. The lid portion 54 can serve as aheat sink for the controller 82 and can include a plurality of fins 84to facilitate dissipation of heat from the controller 82. A heat sinkcompound (not shown), such as thermal paste, for example, can beprovided between the lid portion 54 and the controller 82 to enhance thethermal conductivity therebetween. The main frame 42 and the covermember 44 can each be formed of a thermally conductive material such asaluminum, for example. Heat from the first and second lighting modules24, 26 and the controller 82 can be transmitted throughout the housing22 to effectively supplement the cooling properties of the heat sink 78and the lid portion 54.

Referring now to FIGS. 1 and 2 , the housing 22 can define a passageway85 that extends between the light support portion 30 and the controllersupport portion 32 such that the first and second lighting modules 24,26 and the controller 82 are physically spaced from each other. Thepassageway 85 can be configured to allow air to flow between the lightsupport portion 30 and the controller support portion 32 to enhancecooling of the first and second lighting modules 24, 26 and thecontroller 82 during operation. In one embodiment, as illustrated inFIG. 3 , the housing 22 can comprise a plurality of rib members 86 thatextend between the light support portion 30 and the controller supportportion 32 to provide structural rigidity therebetween.

Referring now to FIG. 6 , the controller 82 can include a power supplymodule 88 and an LED driver module 90. The power supply module 88 can becoupled with the LED driver module 90, and the LED driver module 90 canbe coupled with each of the first and second lighting modules 24, 26(e.g., in parallel). The power supply module 88 can include a powerinput 92 that is coupled with a power source (not shown), such as an A/Cpower source, for delivering external power to the power supply module88 for powering the first and second lighting modules 24, 26. The powersupply module 88 can be configured to condition the external power fromthe power source (e.g., transform AC power to DC power) to facilitatepowering of the LEDs (e.g., 60). In one embodiment, the light fixture 20can be configured to operate at an input power of between about 85 VACand about 347 VAC (e.g., a 750 Watt load capacity).

The LED driver module 90 can include a control input 94 that is coupledwith a control source (not shown), such as a greenhouse controller, forexample, that delivers a control signal to the LED driver module 90 forcontrolling the first and second lighting modules 24, 26, as will bedescribed in further detail below. The LED driver module 90 can beconfigured to communicate according to any of a variety if suitablesignal protocols, such as BACnet, ModBus, or RS485, for example.

The power input 92 and the control input 94 can be routed to a socket 96(FIGS. 2 and 6 ) that is configured to interface with a plug (not shown)that can deliver the external power and control signals to the powersupply module 88 and the LED driver module 90, respectively. In oneembodiment, the socket 96 can be a Wieland-type connector, althoughother connector types are contemplated. It is to be appreciated thatalthough the power and control signals are shown to be delivered throughthe socket 96 (e.g., via the same cable), the light fixture 20 canalternatively include separate ports for the power and the controlsignal such that the power and the control signal are transmitted to thepower supply module 88 and the LED driver module 90 along differentcables.

The LED driver module 90 can be configured to control one or more of theintensity, color, and spectrum of the light generated by the LEDs (e.g.,60) as a function of time (e.g., a light recipe). The LED driver module90 can control the light recipe of the first and second lighting modules24, 26 independently such that the first and second lighting modules 24,26 define respective first and second lighting zones that areindependently controllable within the lighting environment. The lightrecipes of the first and second lighting zones can accordingly betailored to accommodate the lighting requirements of plants that areprovided within the lighting environment. For example, when the plantsprovided in each of the first and second lighting zones are the same (orhave similar lighting requirements), the respective light recipes forthe first and second lighting modules 24, 26 can be the same to providea substantially uniform lighting environment between the first andsecond lighting zones. When a group of plants provided in the firstlighting zone has a different lighting requirement from a group ofplants provided in the second lighting zone, the respective lightrecipes for the first and second lighting modules 24, 26 can be tailoredto accommodate the different lighting requirements between the groups ofplants. In one embodiment, the first and second lighting modules 24, 26can have unique addresses such that the control signal can assignseparate lighting recipes to each of the first and second lightingmodules 24, 26 (via the LED driver module 90) based upon their uniqueaddresses. It is to be appreciated, that although the LED driver module90 is described as being configured to control the light recipe of eachof the first and second lighting modules 24, 26, the LED driver module90 can additionally or alternatively be configured to control any of avariety of suitable alternative variable lighting features of the firstand second lighting modules 24, 26 (e.g., any lighting feature that canbe controlled in real time with a control signal).

The first and second lighting modules 24, 26 can be self-contained,stand-alone units that are physically separate from each other. As such,the physical configuration and variable lighting features of each of thefirst and second lighting modules 24, 26 can be individually selected toallow the first and second lighting zones to be customized to achieve adesired lighting environment. In one embodiment, the first and secondlighting modules 24, 26 can be exchanged with different lighting modulesduring the life cycle of a plant to optimize the lighting environmentfor the plant throughout its life cycle.

FIGS. 7-11 illustrate an alternative embodiment of a lens cover 164 thatcan be similar to, or the same in many respects as, the lens cover 64described above and illustrated in FIGS. 4 and 5 . For example, the lenscover 164 can include a base substrate 168 and a plurality of opticallens elements 170 that protrude from the base substrate 168 and aresubstantially convex-shaped. However, the optical lens elements 170illustrated in FIGS. 7-10 can have a different shape and thus differentoptical characteristics than the optical lens elements 70 illustrated inFIG. 5 .

Referring now to FIGS. 9-11 , one of the optical lens elements 170 willnow be described but can be understood to be representative of the restof the optical lens elements 170 of the lens cover 164. As illustratedin FIGS. 9 and 10 , the optical lens element 170 can include an exteriorsurface 141 and an interior surface 143 that are spaced from each other.The exterior surface 141 and the interior surface 143 can each be acontinuously smooth surface that is devoid of any surfacediscontinuities (e.g., two or more discrete surfaces that are visiblewith the human eye and that are angled relative to each other).

The interior surface 143 can define an interior cavity 145. An LED 160can be at least partially disposed within the interior cavity 145, andan encapsulating material (e.g., 74) can be provided within the interiorcavity 145 such that the encapsulating material (e.g., 74) substantiallyfills the interior cavity 145 and encapsulates the LED 160 therein. TheLED 160 can have a physical center P1, and the optical lens element 170can have a focal center F1 that are substantially coaxial with eachother. In an alternative embodiment, the LED 160 can be slightly offsetwith the optical lens element 170 such that the physical center P1 andthe focal center F1 are non-coaxial. The exterior surface 141 can besubstantially convex shaped and can extend from the base substrate 168along an outer perimeter PR1 (FIG. 11 ). The interior surface 143 can besubstantially convex shaped and can extend from the base substrate 168along an inner perimeter PR2 (FIG. 12 ). The optical lens element 170can have a two-dimensional shape (taken at a cross-section that isorthogonal to the focal center F1) that is substantially rectangular butwith rounded corners. The base substrate 168 can define an annulargroove 169 that extends circumferentially around the optical lenselement 170 and to facilitate releasement of the lens cover 164 form amold when formed via a molding process. The optical lens element 170 canbe substantially symmetrical about the focal center F1.

As illustrated in FIG. 9 , the optical lens element 170 can have alength L1 that extends between opposite sides of the outer perimeter PR1and is orthogonal to the focal center F1. The exterior surface 141 canbe symmetrical about the focal center F1 along the length L1. Theexterior surface 141 can have a central profile 147 that intersects thefocal center F1 and a pair of outer curved profiles 149 that extend fromopposite sides of the central profile 147 to the outer perimeter PR1.The central profile 147 and the pair of outer curved profiles 149 cancooperate to define a lengthwise two-dimensional profile (taken at across-section that is orthogonal to a width W1 (FIG. 10 )) for theexterior surface 141. The central profile 147 can be substantiallyplanar and can be perpendicular to the focal center F1. The centralprofile 147 can extend over about ⅓ the length L1 of the optical lenselement 170 and each of the outer curved profiles 149 can extend overabout ⅓ the length L1 of the optical lens element 170 such that theexterior surface 141 has a flattened, semi-ovular lengthwisetwo-dimensional shape. The exterior surface 141 can be bisected by thefocal center F1 of the optical lens element 170 (relative to the lengthL1) and can have a lengthwise two-dimensional shape that issubstantially symmetric (e.g., entirely symmetric) about the focalcenter F1 (e.g., the exterior surface 141 located on one side of thefocal center F1 is a mirror image of the exterior surface 141 located onthe other side of the focal center F1).

The interior surface 143 can be symmetrical about the focal center F1.The interior surface 143 can include a pair of curved profiles 151 thatextend from opposite sides of the focal center F1 to the inner perimeterPR2. The curved profiles 151 can have a different shape than the outercurved profiles 149. The curved profiles 151 can cooperate to define alengthwise two-dimensional shape (taken at a cross-section that isorthogonal to the width W1) for the interior surface 143 that issubstantially parabolic shaped. In one embodiment, the outer curvedprofiles 149 can have a greater curvature than the curved profiles 151(e.g., a radius of curvature of the outer curved profiles 149 can begreater than a radius of curvature of the curved profiles 151). Theinterior surface 143 can be bisected by the focal center F1 of theoptical lens element 170 (relative to the length L1) and can have alengthwise two-dimensional shape that is substantially symmetric (e.g.,entirely symmetric) about the focal center F1.

The lens cover 164 can define a recess 153 adjacent to the interiorsurface 143 and the interior cavity 145. The recess 153 can beconfigured to capture excess encapsulating material (e.g., 74) that maybe squeezed from the interior cavity 145 when the submount (e.g., 56) ispressed into the lens cover 164 during manufacturing. In one embodiment,the recess 153 can extend circumferentially around the interior surface143. The recess 153 can also enhance demolding of the optical lenselement 170 during manufacturing and can encourage the isolation oflight between adjacent optical lens elements 170.

The exterior surface 141 and the interior surface 143 can cooperate todefine an overall lengthwise two-dimensional shape for the optical lenselement 170 that has a material thickness T1. Because the exteriorsurface 141 and the interior surface 143 have different overalllengthwise two-dimensional shapes, the material thickness T1 at theouter perimeter PR of the optical lens element 170 can be thicker thanthe material thickness T1 at the focal center F1. In one embodiment, thematerial thickness T1 at the focal center F1 can be between about 2 mmand about 3 mm and more particularly about 2.4 mm.

As illustrated in FIG. 10 , the optical lens element 170 can have awidth W1 that extends between opposite sides of the outer perimeter PR1and is orthogonal to the length L1 (FIG. 9 ) and to the focal center F1.The width W1 can be understood to be the narrowest dimension of theoptical lens element 170 measured at the outer perimeter PR1 in adirection that is orthogonal to the focal center F1. The width can benarrower than the length L1. The ratio of the width W1 to the length canbe about 2:3. In one embodiment, the width W1 can be between about 6.5mm and about 7.5 mm and more particularly about 6.9 mm, and the lengthL1 can be between about 8.5 mm and about 10 mm and more particularlyabout 9.3 mm.

The exterior surface 141 can be symmetrical about the focal center F1along the width W1. The exterior surface 141 can be bisected by thefocal center F1 of the optical lens element 170 (relative to the widthW1) and can have a widthwise two-dimensional shape (taken at across-section that is orthogonal to the length L1) that is substantiallysymmetric (e.g., entirely symmetric) about the focal center F1. Theinterior surface 143 can be symmetrical about the focal center F1 alongthe width W1. The interior surface 143 can also be bisected by the focalcenter F1 of the optical lens element 170 (relative to the width W1) andcan have a widthwise two-dimensional shape (taken at a cross-sectionthat is orthogonal to the length L1) that is substantially symmetric(e.g., entirely symmetric) about the focal center F1.

The exterior surface 141 can include a pair of curved profiles 155 thatextend from opposite sides of the focal center F1 to the outer perimeterPR1. The curved profiles 155 can cooperate to define a widthwisetwo-dimensional shape (taken at a cross-section that is orthogonal tothe width W1) for the exterior surface 141 that is substantiallysemicircular shaped. The interior surface 143 can include a pair ofcurved profiles 157 that extend from opposite sides of the focal centerF1 to the outer perimeter PR1. The curved profiles 157 can cooperate todefine a widthwise two-dimensional shape (taken at a cross-section thatis orthogonal to the width W1) for the interior surface 143 that issubstantially semicircular shaped. In one embodiment, the curvedprofiles 155 can have a greater curvature than the curved profiles 157(e.g., a radius of curvature of the curved profiles 155 can be greaterthan a radius of curvature of the curved profiles 157).

The exterior surface 141 and the interior surface 143 can cooperate todefine an overall widthwise two-dimensional shape for the optical lenselement 170 that has a material thickness T2. Because the exteriorsurface 141 and the interior surface 143 have different overallwidthwise two-dimensional shapes, the material thickness T2 at the focalcenter F1 of the optical lens element 170 can be thicker than thematerial thickness T2 at the outer perimeter PR1. In one embodiment, thematerial thickness T2 at the focal center F1 can be between about 2 mmand about 3 mm and more particularly about 2.4 mm.

Referring now to FIGS. 9 and 10 , the outer perimeter PR1 can residewithin a first imaginary plane PL1 and the inner perimeter PR2 canreside within a second imaginary plane PL2. The exterior surface 141 canbe spaced from the first imaginary plane PL1 by a height H1 that ismeasured along the focal center F1. In one embodiment, the height H1 canbe between about 2 mm and about 3 mm and more particularly about 2.5 mm.The interior surface 143 can be spaced from the first imaginary planePL1 by a height H2 that is measured along the focal center F1. In oneembodiment, the height H2 can be between about 0.75 mm and about 1.25 mmand more particularly about 1.0 mm.

Referring now to FIG. 13 , a plurality of imaginary lines 171 can beprovided at different locations on each of the outer curved profiles 149of the exterior surface 141. Each of the imaginary lines 171 can betangent to the outer curved profile 149 such that each imaginary line171 is angled with respect to the first imaginary plane PL1 by an angle173. Each of the outer curved profiles 149 can be sloped (e.g.,contoured) towards respective ones of the central profiles 147 such thatthe angle 173 of each imaginary line 171 is less than the angles 173 ofthe imaginary lines 171 that are more proximate the first imaginaryplane PL1 and greater than the angles 173 of the imaginary lines 171that are more proximate the focal center F1.

A plurality of imaginary lines 175 (one shown) can be provided atdifferent locations on the central profile 147 of the exterior surface141. Each of the imaginary lines 175 can be tangent to the centralprofile 147 such that each imaginary line 175 is angled with respect tothe first imaginary plane PL1 by an angle 177. The central profile 147can be angled (e.g., contoured) upwardly toward the focal center F1 suchthat the angle 177 of each imaginary line 175 is less than or equal tothe angles 177 of the imaginary lines 175 that are more proximate thefirst imaginary plane PL1 and greater than or equal to the angles 177 ofthe imaginary lines 175 that are more proximate the focal center F1.

A plurality of imaginary lines 179 can be provided at differentlocations on each of the curved profiles 151 of the interior surface143. Each of the imaginary lines 179 can be tangent to the curvedprofiles 151 such that each imaginary line 179 is angled with respect tothe second imaginary plane PL2 by an angle 181. Each of the curvedprofiles 151 can be sloped (e.g., contoured) towards the focal center F1such that the angle 181 of each imaginary line 179 is less than theangles 181 of the imaginary lines 179 that are more proximate the secondimaginary plane PL2 and greater than the angles 181 of the imaginarylines 179 that are more proximate the focal center F1. In oneembodiment, the angle 173 of respective ones of the imaginary lines 171that are most proximate to the first imaginary plane PL1 is about 70degrees, the angle 177 of the imaginary lines 175 that are mostproximate to respective ones of the outer curved profiles 149 extendingfrom the central profile 147 is about 3 degrees, and the angle 181 ofrespective ones of the imaginary lines 179 that are most proximate tothe second imaginary plane PL2 is about 71 degrees.

Referring now to FIG. 14 , a plurality of imaginary lines 183 can beprovided at different locations on each of the curved profiles 155 ofthe exterior surface 141. Each of the imaginary lines 183 can be tangentto the curved profile 155 such that each imaginary line 183 is angledwith respect to the first imaginary plane PL1 by an angle 185. Each ofthe curved profiles 155 can be sloped (e.g., contoured) towards thefocal center F1 such that the angle 185 of each imaginary line 183 isless than the angles 185 of the imaginary lines 183 that are moreproximate the first imaginary plane PL1 and greater than the angles 185of the imaginary lines 183 that are more proximate the focal center F 1.

A plurality of imaginary lines 187 can be provided at differentlocations on each of the curved profiles 157 of the interior surface143. Each of the imaginary lines 187 can be tangent to the curvedprofile 157 such that each imaginary line 187 is angled with respect tothe second imaginary plane PL2 by an angle 189. Each of the curvedprofiles 157 can be sloped (e.g., contoured) towards the focal center F1such that the angle 185 of each imaginary line 187 is less than theangles 189 of the imaginary lines 187 that are more proximate the secondimaginary plane PL2 and greater than the angles 189 of the imaginarylines 187 that are more proximate the focal center F1. In oneembodiment, the angle 185 of respective ones of the imaginary lines 183that are most proximate to the first imaginary plane PL1 is about 60degrees, and the angle 189 of respective ones of the imaginary lines 187that are most proximate to the second imaginary plane PL2 is about 71degrees.

Referring again to FIG. 7 , the optical lens elements 170 can beprovided in a grid-like arrangement on the base substrate 168. Eachoptical lens element 170 can cooperate with the underlying LED (e.g.,160) to provide light distribution from each optical lens element 170that is more effective at providing light to underlying plant(s) thanconventional horticultural lighting arrangements. One example of an IESlight distribution plot for the lens cover 164 is illustrated in FIG. 15.

When a plurality of light fixtures (e.g., 20) that incorporate the lenscover 164 are arranged in an indoor growing facility in a similar manneras conventional lighting arrangements (e.g., the same number of lightfixtures and fixture layout as the conventional arrangements), the lightfixtures (e.g., 20) can be more energy efficient, can achieve betterlight uniformity, and can have a higher photosynthetic photon fluxdensity (PPFD) than the conventional lighting arrangements.

The foregoing description of embodiments and examples has been presentedfor purposes of illustration and description. It is not intended to beexhaustive or limiting to the forms described. Numerous modificationsare possible in light of the above teachings. Some of thosemodifications have been discussed and others will be understood by thoseskilled in the art. The embodiments were chosen and described forillustration of various embodiments. The scope is, of course, notlimited to the examples or embodiments set forth herein, but can beemployed in any number of applications and equivalent devices by thoseof ordinary skill in the art. Rather, it is hereby intended that thescope be defined by the claims appended hereto. Also, for any methodsclaimed and/or described, regardless of whether the method is describedin conjunction with a flow diagram, it should be understood that unlessotherwise specified or required by context, any explicit or implicitordering of steps performed in the execution of a method does not implythat those steps must be performed in the order presented and may beperformed in a different order or in parallel.

What is claimed is:
 1. A lens cover for a plurality of light emittingdevices, the lens cover comprising: a base substrate; and an opticallens element that extends from the base substrate and defines a focalcenter, the optical lens element having a length and a width andcomprising: an exterior surface that extends from the base substratealong an outer perimeter, the exterior surface comprising: a firstlengthwise two-dimensional profile taken at a cross-section that isorthogonal to the width at the focal center, the first lengthwisetwo-dimensional profile comprising a central profile and a pair of firstcurved profiles extending from the central profile to the basesubstrate, each of the first curved profiles having a greater curvaturethan the central profile; and a first widthwise two-dimensional profiletaken at a cross-section that is orthogonal to the length at the focalcenter, the first widthwise two-dimensional profile comprising a pair ofsecond curved profiles extending from the focal center; and an interiorsurface comprising: a second lengthwise two-dimensional profile taken ata cross-section that is orthogonal to the width at the focal center, thesecond lengthwise two-dimensional profile comprising a pair of thirdcurved profiles extending from the focal center and each having acurvature that is less than the curvature of the central profile; and asecond widthwise two-dimensional profile taken at a cross-section thatis orthogonal to the length at the focal center, the second widthwisetwo-dimensional profile comprising a pair of fourth curved profilesextending from the focal center and each having a curvature that is lessthan the curvature of the pair of second curved profiles, wherein: thewidth is narrower than the length; the central profile extends over atleast about one third of the length; and the central profile issubstantially planar.
 2. The lens cover of claim 1 wherein: the exteriorsurface and the interior surface cooperate to define an overallwidthwise two-dimensional shape at a cross-section taken orthogonal tothe length at the focal center; and the overall widthwisetwo-dimensional shape has a second material thickness that is thicker atthe focal center than at the outer perimeter.
 3. The lens cover of claim1 wherein the width is the narrowest dimension of the optical lenselement measured at the outer perimeter in a direction that isorthogonal to the focal center.
 4. The lens cover of claim 3 wherein aratio of the width to the length is about 2:3.
 5. The lens cover ofclaim 4 wherein the width is between about 6.5 mm and about 7.5 mm andthe length is between about 8.5 mm and about 10 mm.
 6. The lens cover ofclaim 1 wherein the optical lens element has a substantially rectangularshape but with rounded corners when viewed along the focal center. 7.The lens cover of claim 6 wherein the base substrate defines an annulargroove that extends circumferentially around the optical lens elementadjacent the exterior surface.
 8. The lens cover of claim 1 wherein: theouter perimeter resides within an imaginary plane; the exterior surfaceis spaced from the imaginary plane by a first height that is measuredalong the focal center; the interior surface is spaced from theimaginary plane by a second height that is measured along the focalcenter; the first height is between about 2.0 mm and about 3.0 mm; andthe second height is between about 0.75 mm and about 1.25 mm.
 9. Thelens cover of claim 1 wherein the curvature of the central profile isless than about 3 degrees.
 10. A lens cover for a plurality of lightemitting devices, the lens cover comprising: a base substrate; and anoptical lens element defining a focal center having a length and a widthand comprising: an exterior surface that extends from the base substratealong an outer perimeter that resides within a first imaginary plane,the exterior surface being symmetrical about the focal center, theexterior surface comprising: a first lengthwise two-dimensional profileat a cross-section taken orthogonal to the width at the focal center,the first lengthwise two-dimensional profile comprising a centralprofile and a pair of first curved profiles extending from the centralprofile; and a first widthwise two-dimensional profile at across-section taken orthogonal to the length at the focal center, thefirst widthwise two-dimensional profile comprising a pair of secondcurved profiles extending from the focal center such that the firstwidthwise two-dimensional profile is substantially semicircular shaped;and an interior surface that extends from the base substrate along aninner perimeter that resides within a second imaginary plane, theinterior surface being symmetrical about the focal center, the interiorsurface comprising: a second lengthwise two-dimensional profile at across-section taken orthogonal to the width at the focal center, thesecond lengthwise two-dimensional profile comprising a pair of thirdcurved profiles extending from the focal center; and a second widthwisetwo-dimensional profile at a cross-section taken orthogonal to thelength at the focal center, the second widthwise two-dimensional profilecomprising a pair of fourth curved profiles extending from the focalcenter, wherein: the width is narrower than the length; the centralprofile extends over at least about one third of the length; and thecentral profile is substantially planar.
 11. The lens cover of claim 10wherein the base substrate defines an annular groove that extendscircumferentially around the optical lens element adjacent the exteriorsurface.
 12. The lens cover of claim 10 wherein: the exterior surfaceand the interior surface cooperate to define an overall widthwisetwo-dimensional shape at a cross-section taken orthogonal to the lengthat the focal center; and the overall widthwise two-dimensional shape hasa second material thickness that is thicker at the focal center than atthe outer perimeter.
 13. The lens cover of claim 10 wherein the width isthe narrowest dimension of the optical lens element measured at theouter perimeter in a direction that is orthogonal to the focal center.14. The lens cover of claim 13 wherein a ratio of the width to thelength is about 2:3.
 15. The lens cover of claim 14 wherein the width isbetween about 6.5 mm and about 7.5 mm and the length is between about8.5 mm and about 10 mm.
 16. The lens cover of claim 10 wherein theoptical lens element has a substantially rectangular shape but withrounded corners when viewed along the focal center.
 17. The lens coverof claim 16 wherein the base substrate defines an annular groove thatextends circumferentially around the optical lens element adjacent theexterior surface.
 18. The lens cover of claim 10 wherein: the outerperimeter resides within an imaginary plane; the exterior surface isspaced from the imaginary plane by a first height that is measured alongthe focal center; the interior surface is spaced from the imaginaryplane by a second height that is measured along the focal center; andthe first height is between about 2.0 mm and about 3.0 mm; and thesecond height is between about 0.75 mm and about 1.25 mm.